Scottish scientists report that women living in countries with worse rates of disease and ill health are far likelier to head for masculine-looking men than feminine-looking rivals.

Researchers from the University of Aberdeen wanted to test the hypothesis that masculine traits in men are a sign of genetic health.

If true, this should also have an effect on women, whose choice of a mate is influenced by the chances of their offspring's survival, according to the hypothesis.

The team recruited more than 4500 women in their early twenties in 30 countries via the Internet.

They asked the volunteers to decide which of two faces of the same man was more attractive. Twenty pairs of photos had features morphed to look either square-jawed and masculine, or slim-jawed and feminine.

The finding shows that mating choices may differ according to country and culture, but this is only because of variations in the local environment, says DeBruine. Underneath, women share a similar biological drive.

In previous research, DeBruine found that women who were more easily disgusted by cues of pathogens (such as men with open sores) were also likelier to prefer masculine-type fellows.

Downside

Manliness, though, is only part of a complex equation when it comes to mating.

A woman in an unhealthy environment may prefer a macho man as a sign of genetic wellbeing, but she may not see him as a good bet for bringing up her children.

"Indeed, there is compelling evidence that women ascribe antisocial traits and behaviours to masculine men," says the study, published in the journal Proceedings of the Royal Society B.

"Women perceive masculine men as dishonest, uncooperative, more interested in short-term than long-term relationships, and even as 'bad parents'."

Other factors add to the complex mating mix.

During the most fertile, hormone-laden phase of her menstrual cycle, a woman is more likely to prefer masculine men. Social equality and control of resources can also shape perceptions about male attractiveness.

The study participants came from countries in which Caucasians are in the majority, ranging from low-income economies in Eastern Europe such as Russia and Romania, to Canada and the United States.

Participants gave their ethnicity as white, as were the faces that were shown to them.

The researchers say they chose a single ethnicity in order to get a clearer signal from the respondents.